(1R,5S,7S,8R,12S,13S)-12,13-Dihydroxy-1,8-bis(hydroxymethyl)-6-azadispiro[4.1.4.2]tridecane-6-oxyl - a Chiral Hydrophilic Dispirocyclic Radical with High Stability to Reduction

Modern trends in the development of structural biology make it relevant to study the structure of biomolecules under the conditions close to natural, i.e., directly in a living cell and at temperatures close to physiological ones. One of the promising technologies that allows approaching this ideal is the targeted introduction of spin labels (for example, nitroxides), followed by investigation using pulsed electron paramagnetic resonance (EPR). Today, the greatest stability in living systems is demonstrated by sterically hindered nitroxyl radicals of the pyrrolidine series with four ethyl groups at a paramagnetic centre, but their relaxation characteristics do not allow measurements by pulsed ESR methods at a temperature above 80 K. Nitroxides with spirocycloalkane fragments surrounding the nitroxyl group are suitable for measurements at higher temperatures, but they are rapidly reduced by the components of living systems. Pyrrolidine nitroxides with two spiro-(2-hydroxymethyl)cyclopentane moieties combine high resistance to reduction with high spin relaxation times at a temperature of 120 K and above. In this work, a hydrophilic chiral radical of this series - (1R,5S,7S,8R,12S,13S)-12,13-dihydroxy-1,8- bis(hydroxymethyl)-6-azadispiro[4.1.4.2]tridecane-6-oxyl was obtained and characterised by us for the first time.